Fuel vapor storage canisters have become standard pieces of equipment on vehicles for the recovery and storage of fuel emissions. Generally, fuel vapor canisters include an elongated canister containing a bed of fuel adsorbent material, such as activated carbon. Air containing fuel vapors enters the fuel storage canister from a tube connected to the vehicle's fuel tank. The fuel vapors are adsorbed into the bed of carbon and the filtered air is released into the atmosphere. Later, the fuel vapors are desorbed by the carbon and vented through a purge line to the engine.
During its life a fuel vapor storage canister may be exposed to a wide temperature range that may cause the canister to expand and contract, varying the volume of the interior of the canister. The canister may also be exposed to vibration and motion, which may shift the carbon in the canister. This vibration and thermal expansion and contraction may cause the carbon particles to erode against one another. Erosion of the carbon particles creates flow paths through which the vapor may escape without being properly adsorbed by the carbon. Accordingly, fuel vapor storage canisters typically include a volume compensator to securely pack the activated carbon contained within the canister.
Existing volume compensators compact the carbon bed through a plate biased against the bed of activated carbon by one or more coil springs, as shown in FIG. 1. The use of multiple springs is costly and complicates the assembly process. Additionally, individual variances in the springs cause uneven pressure against the grid.
Accordingly, a new volume compensator design is desired.